9

FN6581.1

November 3, 2009

Detailed Description

The ISL54062 is a bi-directional, dual single pole-double

throw (SPDT) analog switch that offers precise switching

from a single 1.8V to 6.5V supply with low ON-resistance

(0.83

negative signal swing capability. The device is especially

well suited for portable battery powered equipment due to its

low operating supply voltage (1.8V), low power consumption

(20nA @ 3V), and a tiny 1.8mmx1.4mm µ

TQFN package or a

provide very low insertion loss and signal distortion for

applications that require signal switching with minimal

interference by the switch.

Supply Sequencing and Overvoltage Protection

With any CMOS device, proper power supply sequencing is

required to protect the device from excessive input currents

which might permanently damage the IC. The ISL54062

contains ESD protection diodes on each pin of the IC

(see Figure 9). These diodes connect to either a +Ring or

-Ring for ESD protection. To prevent forward biasing the

ESD diodes to the +Ring, V+ must be applied before any

input signals, and the input signal voltages must remain

between recommended operating range.

If these conditions cannot be guaranteed, then precautions

must be implemented to prohibit the current and voltage at

the logic pin and signal pins from exceeding the maximum

ratings of the switch. The following two methods can be used

to provided additional protection to limit the current in the

event that the voltage at a logic pin or switch terminal goes

above the V+ rail.

Logic inputs can be protected by adding a 1k

Ω resistor in

series with the logic input (see Figure 9). The resistor limits

the input current below the threshold that produces

permanent damage.

This method is not acceptable for the signal path inputs.

Adding a series resistor to the switch input defeats the

external Schottky diodes from the V+ rail to the signal pins

will shunt the fault current through the Schottky diode

instead of through the internal ESD diodes, thereby

protecting the switch. These Schottky diodes must be sized

to handle the expected fault current.

Power-Supply Considerations

The ISL54062 construction is typical of most single supply

CMOS analog switches which have two supply pins: V+ and

GND. V+ and GND provide the CMOS switch bias and sets

their analog voltage limits. Unlike switches with a 5.5V

maximum supply voltage, the ISL54062’s 6.5V maximum

supply voltage provides plenty of head room for the 10%

tolerance of 5V supplies due to overshoot and noise spikes.

FIGURE 8A. CLICK AND POP WAVEFORM

FIGURE 8B. CLICK AND POP TEST CIRCUIT

FIGURE 8. CLICK AND POP ELIMINATION

0V

0V

CLICK AND POP

CIRCUITRY

220uF

220uF

INx

COMx

NCx

NOx

GND

V+

LOGIC

INPUTS

-RING

+RING

CLAMP

1k

Ω

FIGURE 9. OVERVOLTAGE PROTECTION

ISL54062